This invention relates generally to the removal of non-condensible gases from a refrigeration system and particularly to a device for sensing such gases and purging them from a refrigerant purification system.
Chlorofluorocarbons (CFC's) have been used since their discovery in 1928 for many purposes. In addition to being used as a refrigerant they are used to make foam insulation and, up until 1978 were the most common and successful gas used as the propellant in aerosol cans. They perform better than all known substitutes but, unfortunately, have a dangerous disadvantage. When they are released into the atmosphere they float upwardly and the chlorine in them destroys the ozone layer that protects the earth against the damaging ultraviolet light rays of the sun.
It is the aim of refrigerant industry to ban CFC's completely within ten years. The most promising substitutes are the Hydrofluorocarbons (HCFC's). In particular, HCFC-22 is viewed as part of a long-term solution but it is clear that much work will be required before this gas can be substituted for the immense number of refrigerant applications using CFC's in the equipment service industry, especially in view of the fact that the HCFC's will require new equipment specifically designed for use with HCFC's.
One of the most damaging of the CFC refrigerants is CFC-12, one which creates less damage is CFC-502. A proposal has been made that a practical solution would be to eliminate CFC-12 as soon as possible and reduce production of CFC-502 by means of effective recycling and other conservation practices. An effective recycling program will provide that existing equipment using CFC's can be maintained for much of its remaining life and will eliminate the need for expensive conversion of existing systems to a new refrigerant.
There are obstacles to recycling and one of the most serious is the presence of non-condensible gases in the system which render the refrigerant undersirable for continued use. Refrigerant contained within a refrigeration system has a characteristic known as its saturation curve which relates a specific temperature to a specific pressure as long as refrigerant is present in both liquid and vapor stages. The presence of non-condensible gases, such as air, within the system offsets the saturation curve due to partial pressure of such gases and detrimentally affects the saturation pressure of the refrigerant.
One of the problems associated with non-condensible gas contamination is that the high pressure side of a refrigeration system operates at a higher than normal pressure increasing the compression ratio, heat of compression and gas discharge temperature causing inefficient compressor operation and even compressor failure. Another problem is that the entrapped non-condensible gas contains oxygen which can reduce hydrocarbons and produce oil breakdown to form acids which can also cause compressor failure.
These, and associated problems not only result in ineffective operation of the refrigeration system but also render the refrigerant less useful for recycling. Accordingly, there is a need for an automatic device which not only senses the presence of non-condensible gases but which purges these gases to atmosphere. Manually operated refrigerant purging systems are known which use a pressure gauge and simple bleed valve. The bleed valve is opened from time to time and if non-condensible gas is present it escapes and the pressure gauge drops. This procedure is followed until the pressure gauge reading stabilizes. This system not only suffers the disadvantage of being manual but is wasteful because it permits the escape of refrigerant when non-condensible gas is not present.
The present invention solves these and other problems in manner not revealed in the known prior art.